The present invention is directed to an electrical box having a metal ground strap. More particularly, the invention is directed to a non-metallic electrical box having a metallic ground strap fixed to the electrical box for grounding an electrical device.
Electrical boxes as known in the art are commonly used for supporting and enclosing electrical switches, connectors, receptacles and other electrical devices. The electrical boxes generally include suitable mounting hardware for mounting the box to a suitable support structure. The electrical boxes also include screw holes and mounting threads for mounting the electrical device within the box, and have various openings for feeding wires or cables into the electrical box.
In the past, electrical boxes were made exclusively of metal. Metal electrical boxes have the advantage that the boxes can be grounded directly to a ground wire. The electrical device, when attached to the metal electrical box, can be adequately grounded through the electrical box as well as by a standard ground wire.
In recent years, many electrical boxes have been made of plastic materials since they are lightweight, inexpensive and easily manufactured. Since plastic and other non-metallic materials used for making electrical boxes cannot be directly grounded, a suitable grounding system must be provided. Typically, a ground wire is passed through the electrical box and attached directly to the electrical device. However, since some electrical codes require the electrical box to be grounded, a grounding member is often coupled to the electrical box which can then be connected to a ground wire.
Non-metallic electrical boxes have also been provided with a metallic ground strap that is attached to the electrical box. One example of such a device is disclosed in U.S. Pat. No. 3,210,458 to Palmer. In this device, a metallic ground strap is attached to the side wall of the electrical box. The ground strap has a top end with an opening for receiving a screw or other fastener for attaching directly to the electrical device. The bottom end of the ground strap has a tab that extends through an opening in the bottom wall of the electrical box and is bent to secure the ground strap in place. The bottom end of the ground strap also includes a threaded hole for receiving a screw for attaching to a grounding wire.
Another form of ground strap is disclosed in U.S. Pat. No. 4,315,100 to Haslbeck et al. This device includes a non-metallic electrical box having a ground strap attached to the top end of the electrical box. The ground strap includes an opening for receiving a threaded fastener for coupling directly to the electrical box. A second threaded opening is provided at the opposite end of the ground strap for receiving a fastener for coupling directly to a ground wire.
The prior devices can be effective for grounding a single electrical device, but are not sufficient for grounding several electrical devices simultaneously. In addition, these devices can be difficult to assemble and do not comply with some electrical codes.
In view of the deficiencies of the prior electrical boxes and grounding systems, there is a continuing need in the industry for improved non-metallic electrical boxes.
The present invention is directed to a non-metallic electrical box having a metal ground strap. More particularly, the invention is directed to an electrical box having a ground strap for grounding an electrical device mounted in the box. Accordingly, a primary object of the invention is to provide an electrical box assembly including an electrical box and a ground strap where the ground strap is coupled directly to the electrical box.
Another object of the invention is to provide an electrical box assembly having an electrical box and a ground strap where the ground strap can be coupled to the electrical box without the use of fasteners or adhesives.
A further object of the invention is to provide an electrical box assembly having an electrical box and a ground strap where the ground strap is coupled to the electrical box by an interference fit.
Still another object of the invention is to provide an electrical box assembly having an electrical box and a ground strap where the electrical strap is wedged between two opposing surfaces formed in the electrical box for coupling the ground strap to the electrical box.
A further object of the invention is to provide an electrical box assembly having an electrical box and a ground strap where the ground strap includes a pair of coupling tabs for engaging opposing surfaces on the electrical box for attaching the ground strap to the electrical box.
Another object of the invention is to provide an electrical box assembly having an electrical box and a ground strap where the bottom wall of the electrical box includes a raised portion for supporting the ground strap so that one end of the ground strap is cantilevered with respect to the raised portion.
A further object of the invention is to provide an electrical box assembly having an electrical box and a ground strap being cantilevered with respect to a bottom wall to provide a spring action to assist in the ground strap wedging between two opposing coupling members.
Another object of the invention is to provide an electrical box assembly having an electrical box and a plurality of ground straps coupled to the electrical box and a connecting strap extending between each of the ground straps and coupled to the ground straps by a snap connection.
Still another object of the invention is to provide an electrical box assembly including an electrical box, a plurality of ground straps and a connecting strap having coupling devices for attaching to each of the ground straps.
The foregoing objects of the invention are basically attained by providing an electrical box assembly comprising: an electrical box having a bottom wall, a first end wall, and a second end wall. The first end wall has a coupling member with two spaced-apart opposing flanges extending inwardly into a cavity of the electrical box. Each of the flanges has an undercut portion in an opposing outer edge extending in a generally upward direction with respect to the bottom wall. A metallic ground strap has a length and a width. The ground strap is wedged between the opposing outer edge of the flanges to retain the ground strap against the bottom wall.
The objects and advantages of the invention are further attained by providing an electrical box assembly comprising: a non-metallic electrical box having a bottom wall, a first end wall and a second end wall, and a coupling member having two opposing coupling tabs on the bottom wall. A metallic ground strap has opposite side edges, each of the side edges has a coupling tab spaced from a first end of the ground strap. Each of the coupling tabs of the ground strap engages the coupling tabs of the electrical box.
The foregoing objects of the invention are further attained by providing an electrical box assembly comprising: a non-metallic electrical box having a bottom wall, a first end wall, a second end wall, and a plurality of coupling members, each of said coupling members having two opposing coupling tabs; a metallic ground strap coupled to each of said coupling members of said electrical box, each metallic ground strap positioned adjacent said bottom wall, said ground strap having opposite side edges, each of said side edges having a coupling tab spaced from a first end of said ground strap, and each of said coupling tabs of said ground strap engaging said coupling tabs of said electrical box for coupling said ground strap to said electrical box; and a metallic coupling member coupled to each of said ground straps.
The objects, advantages and other salient features of the invention will become apparent from the following detailed description in conjunction with the annexed drawings which form a part of this original disclosure.